Nanocrystals of polycrystalline layered lithium nickel metal oxides

ABSTRACT

Provided are electrochemically active secondary particles that provide excellent capacity and improved cycle life. The particles are characterized by a plurality of nanocrystals with small average crystallite size. The reduced crystallite size reduces impedance generation during cycling thereby improving capacity and cycle life. Also provided are methods of forming electrochemically active materials, as well as electrodes and electrochemical cells employing the secondary particles.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/481,719 filed Sep. 22, 2021, which is a continuation of U.S. Ser. No.16/096,403, filed Oct. 25, 2018 (now U.S. Pat. No. 11,158,853), andwhich is a U.S. National Phase Application under 35 U.S.C. § 371 ofinternational application PCT/US2017/029913 filed Apr. 27, 2017, andwhich claims priority of U.S. Patent Application Ser. No. 62/328,447filed Apr. 27, 2016, the disclosure of each of which is incorporatedherein by reference.

FIELD

Disclosed is polycrystalline metal oxide particle, methods ofmanufacture thereof, and electrochemical cells or batteries comprisingthe same.

BACKGROUND

Layered structure lithium nickelate (LiNiO₂)-based materials have beendeveloped for Lithium-ion battery cathodes because they generally havelower cost, higher capacity and higher rate capability than thehistorically predominant LiCoO₂ cathode material. However, pure LiNiO₂materials exhibit poor electrochemical stability and cyclingperformance. To address this, non-nickel, elemental additives have beenformulated into LiNiO₂ that stabilize the structure improving thecycling performance, but typically at the expense of discharge capacity.As demands for energy density have increased, research has focused onoptimizing and reducing these non-nickel additives to capture thecapacity of high Ni materials while at the same time maintaining cyclingperformance.

As such, new materials are needed to address the demands for highcapacity materials with long cycle life. The materials provided hereinand methods of forming such materials address this need by maintaininghigh capacity over a long cycle life.

SUMMARY

The following summary is provided to facilitate an understanding of someof the innovative features unique to the present disclosure and is notintended to be a full description. A full appreciation of the variousaspects of the disclosure can be gained by taking the entirespecification, claims, drawings, and abstract as a whole.

Provided are electrochemically active polycrystalline particles thatwhen incorporated into a lithium ion cell display excellent capacity andimproved cycle life. The electrochemically active polycrystallineparticle includes a plurality of nanocrystals where the plurality ofnanocrystals includes a first composition defined by Li_(1+x)MO_(2+y).Optionally, x is greater than or equal to −0.1 and less than or equal to0.3. Optionally, y is greater than or equal to −0.3 and less than orequal to 0.3. Optionally, M comprises nickel at greater than or equal to10 atomic percent. The plurality of nanocrystals having an averagecrystallite size of less than or equal to 85 nanometers as determined byx-ray diffraction (XRD) for base particles, or having an averagecrystallite size of less than or equal to 105 nanometers as determinedby XRD for coated or grain boundary enriched particles. In some aspects,M further includes one or more elements selected from the groupconsisting of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Zr, Cr, Mo, Fe, V, Si, Gaand B.

Also provided are methods of manufacturing an electrochemically activepolycrystalline particle where the methods include providing a firstmixture and calcining the first mixture. The first mixture (a “greenbody”) optionally includes lithium hydroxide or its hydrate and aprecursor hydroxide having nickel. Calcining the first mixture includesa maximum temperature of less than 700° C. to form a first materialincluding a plurality of nanocrystals having a size of less than orequal to 85 nanometers. A method optionally further includes coating theparticles and subjecting them to a second calcination to enrich grainboundaries between the nanocrystals/grain. For the coated particles theaverage crystallite size is 105 nm or less.

The resulting particles and methods achieve the objects by providingmaterials the produce electrochemical cells with excellent capacity andimproved cycle life relative to particles with larger crystals.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects set forth in the drawings are illustrative and exemplary innature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrative aspectscan be understood when read in conjunction with the following drawings,where like structure is indicated with like reference numerals and inwhich:

FIG. 1 is a schematic perspective view of a cross-section ofelectrochemically active polycrystalline particle according to one ormore aspects described herein;

FIG. 2 is a graph depicting discharge performance of cathode materialswith large (109 nm) and small crystallite size (78 nm) between cycles100 and 200 for duplicate cells according to one or more aspectsdescribed herein;

FIG. 3 is a graph depicting impedance values for duplicate cellscontaining cathode materials with large and small crystals correspondingto the discharge performance data shown in FIG. 3 according to one ormore aspects described herein; and

FIG. 4 is a graph depicting impedance values between cycles 100 and 200for duplicate cells containing cathode materials having a range ofcrystallite sizes formed through calcination at temperatures of 700degrees Celsius or less according to one or more aspects describedherein.

DETAILED DESCRIPTION

The following description of particular aspect(s) is merely exemplary innature and is in no way intended to limit the scope of the disclosure,its application, or uses, which may, of course, vary. The materials andprocesses are described with relation to the non-limiting definitionsand terminology included herein. These definitions and terminology arenot designed to function as a limitation on the scope or practice of thedisclosure, but are presented for illustrative and descriptive purposesonly. While the processes or compositions are described as an order ofindividual steps or using specific materials, it is appreciated thatsteps or materials may be interchangeable such that the description ofthe invention may include multiple parts or steps arranged in many waysas is readily appreciated by one of skill in the art.

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various aspects areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the aspects set forth herein.Rather, these aspects are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventionto those skilled in the art. Like reference numerals refer to likeelements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element, or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer, or section from another element, component,region, layer, or section. Thus, unless specified otherwise, “a firstelement,” “component,” “region,” “layer,” or “section” discussed belowcould be termed a second (or other) element, component, region, layer,or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof. The term “or a combination thereof” means a combinationincluding at least one of the foregoing elements.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Ni-based layered materials of the LiMO₂ type are dense, polycrystallineagglomerates of primary crystals. These are typically made usingstandard solid-state processes at temperatures in the range of 700° C.to 900° C. starting from a variety of precursor materials. Precursormaterials are typically transition metal hydroxides (M(OH)₂), lithiumprecursors (e.g., LiOH or Li₂CO₃), or inorganic precursors for otherdopants (e.g., hydroxides, carbonates, nitrates). During heating of theprecursor mixture, polycrystalline LiMO₂ is formed along with theexpulsion of gases such as H₂O, CO₂ or NO₂. Simultaneously, the primarycrystals in the polycrystalline material ‘sinter’ into larger primarycrystals. The rate of crystal growth during the high-temperaturesynthesis increases dramatically with an increase in temperature. Thiseffect has fundamental, thermodynamic explanations and is expected;however, the inventors found that the impact on cycling performance isnegative.

During investigation, the inventors found that larger primary crystalstend to increase the rate of impedance growth in the cathode duringrepeated charge/discharge operation (cycling) of the Li-ion battery. Thepower delivery capability of the Li-ion battery reduces with an increasein the impedance of the cathode, and hence is undesirable for normalbattery operation. There are multiple possible explanations for thefaster rate of impedance growth with larger crystals. For example, it isknown that with repeated charge/discharge cycling, the surface of theprimary crystals undergoes damage causing an increase in the resistanceto lithium transport (i.e., an increase in impedance) into the crystalfrom the crystal grain boundary. For a given battery operating current,the lithium flux or the current per unit surface of the crystal will behigher for the larger crystals than the smaller crystals (i.e., arealcurrent density). Even if the resistance increase per unit surface areaof the crystal is the same for smaller and larger crystals, the higherareal current density for the larger crystals results in a highervoltage drop, which is manifest as a higher impedance.

However, active materials that displays a combination of high initialdischarge capacity and low impedance growth during cycling are difficultto make synthetically. This becomes especially true when the nickelcomponent of M approaches 90% and higher. At such levels of nickel, therate of crystal growth at synthetic temperatures required to obtain ahigh degree of crystal order is very high. Primary crystals with a sizesubstantially exceeding 100 nm, often on the order of several hundrednanometers (nm) or more are typical (as determined from X-raydiffraction) with previously known synthetic conditions.

Accordingly, this disclosure addresses the aforementioned difficultiesby providing positive electrode (cathode) active materials for Li-ionbatteries with nanocrystals in order to reduce the rate of impedancegrowth during charge/discharge cycling of the battery. Provided are avariety of methods for achieving high discharge capacity cathode activematerial having an average crystallite size of less than or equal to 85nm for base particle material and less than or equal to 105 nm for grainboundary enriched material (both as determined by XRD) in nickelcontaining formulations.

The polycrystalline layered-structure lithiated metal oxides havingnano-crystalline structure as described herein exhibit enhancedelectrochemical performance and stability. The nano-crystallinecompositions prevent the performance degradation of electrochemicallycycled Ni-containing polycrystalline LiMO₂-based materials, whilemaintaining other desirable end-use article properties, e.g.,electrochemical capacity of rechargeable lithium-ion cathodes made fromsuch nano-crystalline layered metal oxides by reducing the rate ofimpedance growth during electrochemical cycling. Such nano-crystallinecompositions may be readily manufactured by calcining a green bodyformulation including a LiOH and a precursor hydroxide or carbonate to amaximum temperature of less than 700 degrees Celsius.

As such, provided are compositions, systems, and methods of making andusing polycrystalline layered-structure lithiated metal oxides havingnano-crystalline structure in lithium-ion secondary cells as the meansof achieving high initial discharge capacity and low impedance growthduring cycling, thereby overcoming the above-described challenges ofachieving nanocrystals having an average size of less than or equal to105 nm in high-nickel formulations that also have high dischargecapacity (e.g., >205 mAh/g at C/20).

Throughout this disclosure reference is made to the crystallite size ofnanocrystals within the polycrystalline materials. These sizes are asdetermined by XRD methods, optionally by powder X-ray diffractionpatterns collected from a continuous scan between 12 and 120 degrees in2-theta at 0.75 degrees/min using an automated Shimadzu XRD-6000diffractometer with a Cu X-ray tube. As used herein, the term“nanocrystal” refers to a crystallite size of 85 nm or lower for a basematerial and 105 nm or lower for a grain boundary enriched material atrelatively low Co enrichment. It was found that during a coating step toenrich the grain boundaries with cobalt, that crystallite size mayincrease slightly due to high temperature exposure in calcination. Insuch circumstances, the measured crystallite size by XRD is increasedresulting in a material with a measured crystallite size of 105 nm orbelow.

FIG. 1 depicts (not to scale) a schematic of an exemplarypolycrystalline layered-structure lithiated metal oxides havingnano-crystalline structure. The material includes a particle comprisinga plurality of nanocrystals 10 each comprising a first composition. Theparticle with a plurality of nanocrystals may be referred to as asecondary particle. The particles as provided herein are uniquelytailored to have nanocrystals far smaller than those thought suitable inthe art. For example, the particles as provided herein include aplurality of nanocrystals with an average crystallite size of 85nanometers (nm) or less for a base material. The reduced crystallitesize provided for reduced impedance growth during cycling improvingperformance and cycle life of a cell incorporating the particles as acomponent of a cathode. FIG. 1 further illustrates a particular set ofaspects wherein the particles may further include a grain boundary 20formed of or including a second composition, wherein a concentration ofcobalt, for example, in the grain boundary is greater than aconcentration of cobalt, for example, in the nanocrystal. The grainboundary enriched particles as provided herein include a plurality ofnanocrystals with an average crystallite size of 105 nanometers (nm).Optionally, also as depicted in FIG. 1 , an layer 30 may be disposed onan outer surface of the secondary particle to provide a coated secondaryparticle.

In some aspects of the presently provided particles, the firstcomposition includes polycrystalline layered-structure lithiated metaloxides defined by composition Li_(1+x)MO_(2+y) and optionally a cell orbattery formed therefrom, where −0.1≤x≤0.3 and −0.3≤y≤0.3. In someaspects, x is −0.1, optionally 0, optionally 0.1, optionally 0.2, oroptionally 0.3. Optionally, x is greater than or equal to −0.10, −0.09,−0.08, −0.07, −0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0.00, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13,0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25,0.26, 0.27, 0.28, 0.29, or 0.30. In some aspects, y is −0.3, optionally−0.2, optionally −0.1, optionally 0, optionally 0.1, optionally 0.2, oroptionally 0.3. Optionally, y is greater than or equal to −0.30, −0.29,−0.28, −0.27, −0.26, −0.25, −0.24, −0.23, −0.22, −0.21, −0.20, −0.19,−0.18, −0.17, −0.16, −0.15, −0.14, −0.13, −0.12, −0.11, −0.10, −0.09,−0.08, −0.07, −0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0.00, 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13,0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25,0.26, 0.27, 0.28, 0.29, or 0.3.

It is appreciated that in some aspects Li need not be exclusively Li,but may be partially substituted with one or more elements selected fromthe group consisting of Mg, Na, K, and Ca. The one or more elementssubstituting Li, are optionally present at 10 atomic % or less,optionally 5 atomic % or less, optionally 3 atomic % or less, optionallyno greater than 2 atomic percent.

M as provided in the first composition includes Ni. The amount of Ni isoptionally from 10 atomic percent to 99 atomic percent (at %) of M.Optionally, the Ni component of M is greater than or equal to 75 at %.Optionally, the Ni component of M is greater than or equal to 80 at %.Optionally, the Ni component of M is greater than or equal to 85 at %.Optionally, the Ni component of M is greater than or equal to 90 at %.Optionally, the Ni component of M is greater than or equal to 95 at %.Optionally, the Ni component of M is greater than or equal to 75 at %,76 at %, 77 at %, 78 at %, 79 at %, 80 at %, 81 at %, 82 at %, 83 at %,84 at %, 85 at %, 86 at %, 87 at %, 88 at %, 89 at %, 90 at %, 91 at %,92 at %, 93 at %, 94 at %, 95 at %, 96 at %, 98 at %, or 99 at %.

In some aspects, M is Ni and one or more additional elements. Theadditional elements are optionally metals. Optionally, an additionalelement may include or be one or more of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti,Zr, Y, Cr, Mo, Fe, V, Si, Ga, or B. In particular aspects, theadditional element may include Mg, Co, Al, or a combination thereof.Optionally, the additional element may be Mg, Al, V, Ti, B, Zr, or Mn,or a combination thereof. Optionally, the additional element consists ofMg, Al, V, Ti, B, Zr, or Mn. Optionally, the additional element consistsof Mg, Co, and Al. Optionally, the additional element consists of Mg,Co, Al, and Zr. Optionally, the additional element consists of Ca, Co,and Al. In some aspects, the additional element is Mn or Mg, or both Mnand Mg.

An additional element of the first composition may be present in anamount of about 1 to about 90 at %, specifically about 5 to about 80 at%, more specifically about 10 to about 70 at % of the first composition.Optionally, the additional element may be present in an amount of about1 to about 20 at %, specifically about 2 to about 18 at %, morespecifically about 4 to about 16 at %, of the first composition. In someillustrative examples, M is about 75-99 at % Ni, 3-15 at % Co, 0-15 at %Mn, and 0-10 at % additional elements.

Within the polycrystalline material, each nanocrystal may have anysuitable shape, which can be the same or different within each particle.Further, the shape of each nanocrystal can be the same or different indifferent particles. Because of its crystalline nature, the nanocrystalmay be faceted, the nanocrystal may have a plurality of flat surfaces,and a shape of the nanocrystal may approximate a geometric shape. Insome aspects, the nanocrystal may be fused with neighboring nanocrystalswith mismatched crystal planes. The nanocrystal may have a rectilinearshape, and when viewed in cross-section, a portion of or an entirety ofthe nanocrystal may be rectilinear. The nanocrystal may be square,hexagonal, rectangular, triangular, or a combination thereof.

In some aspects referring to a base material that is not enriched in thegrain boundary, the average crystallite size of the nanocrystals is lessthan or equal to about 85 nm. Optionally, the average crystallite sizeof the nanocrystals is less than or equal to about 80 nm. Optionally,the average crystallite size of the nanocrystals is less than or equalto about 75 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 70 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 65 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 60 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 55 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 50 nm.

In some aspects referring to a base material that is not enriched in thegrain boundary, the average crystallite size of the nanocrystals isgreater than or equal to 50 nm to less than or equal to about 85 nm.Optionally, the average crystallite size of the nanocrystals is greaterthan or equal to about 50 nm to less than or equal to about 80 nm.Optionally, the average crystallite size of the nanocrystals is greaterthan or equal to about 50 nm to less than or equal to about 70 nm.Optionally, the average crystallite size of the nanocrystals is greaterthan or equal to about 55 nm to less than or equal to about 70 nm.

In other aspects referring to a base material that is not enriched inthe grain boundary, the average crystallite size of the nanocrystals isless than or equal to about 85 nm, about 84 nm, about 83 nm, about 82nm, about 81 nm, about 80 nm, about 79 nm, about 78 nm, about 77 nm,about 76 nm, about 75 nm, about 74 nm, about 73 nm, about 72 nm, about71 nm, about 70 nm, about 69 nm, about 68 nm, about 67 nm, about 66 nm,about 65 nm, about 64 nm, about 63 nm, about 62 nm, about 61 nm, about60 nm, about 59 nm, about 58 nm, about 57 nm, about 56 nm, about 55 nm,about 54 nm, about 53 nm, about 52 nm, about 51 nm, or about 50 nm.

As measured by XRD for a coated material comprising secondary particleswith metal enriched grain boundaries such as a Co enriched grainboundaries, the average crystallite size of the nanocrystals is lessthan or equal to about 105 nm. Optionally, the average crystallite sizeof the nanocrystals is less than or equal to about 100 nm. Optionally,the average crystallite size of the nanocrystals is less than or equalto about 95 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 90 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 85 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 80 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 75 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 70 nm.

In some aspects referring to grain boundary enriched material, theaverage crystallite size of the nanocrystals is greater than or equal to70 nm to less than or equal to about 105 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about70 nm to less than or equal to about 100 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about70 nm to less than or equal to about 90 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about75 nm to less than or equal to about 90 nm.

In other aspects referring to a grain boundary enriched material, theaverage crystallite size of the nanocrystals is less than or equal toabout 105 nm, about 104 nm, about 103 nm, about 102 nm, about 101 nm,about 100 nm, about 99 nm, about 98 nm, about 97 nm, about 96 nm, about95 nm, about 94 nm, about 93 nm, about 92 nm, about 91 nm, about 90 nm,about 89 nm, about 88 nm, about 87 nm, about 86 nm, about 85 nm, about84 nm, about 83 nm, about 82 nm, about 81 nm, about 80 nm, about 79 nm,about 78 nm, about 77 nm, about 76 nm, about 75 nm, about 74 nm, about73 nm, about 72 nm, about 71 nm, or about 70 nm.

As compared to a base particle, a grain boundary enriched particleincludes Co enrichment in the grain boundary relative to thenanocrystal. The presence of Co enrichment can artificially suppress themeasurement of nanocrystal size when measured using XRD with increasedsuppression in XRD measurement at increasing enrichment levels of Co inthe grain boundaries. For example, the crystallite size for a materialwhere 6 at % Co (relative to the metal content of the base material) isadded to the coating to create a grain boundary-enriched material (6 at% Co enrichment) is smaller than the crystallite size for a materialwith 4 at % Co enrichment. As such, for coated particles, themeasurement of nanocrystal size is optionally at a particular enrichmentlevel of Co. In some aspects, the nanocrystal size at an enrichment of 4at % Co is 105 nm or lower or any other level as in the forgoingparagraphs. Optionally, at a 6 at % enrichment of Co in the grainboundary the nanocrystal size is 80 nm or less or any other value asotherwise described herein less than 80 nm.

In some aspects, the grain boundaries are enriched with Co to 4 at % andthe average crystallite size of the nanocrystals is less than or equalto about 105 nm, about 104 nm, about 103 nm, about 102 nm, about 101 nm,about 100 nm, about 99 nm, about 98 nm, about 97 nm, about 96 nm, about95 nm, about 94 nm, about 93 nm, about 92 nm, about 91 nm, about 90 nm,about 89 nm, about 88 nm, about 87 nm, about 86 nm, about 85 nm, about84 nm, about 83 nm, about 82 nm, about 81 nm, about 80 nm, about 79 nm,about 78 nm, about 77 nm, about 76 nm, about 75 nm, about 74 nm, about73 nm, about 72 nm, about 71 nm, or about 70 nm.

In some aspects, the grain boundary is enriched with about 6 at % cobaltand the average crystallite size of the nanocrystals is less than orequal to about 82 nm, about 81 nm, about 80 nm, about 79 nm, about 78nm, about 77 nm, about 76 nm, about 75 nm, about 74 nm, about 73 nm,about 72 nm, about 71 nm, about 70 nm, about 69 nm, about 68 nm, about67 nm, about 66 nm, about 65 nm, about 64 nm, about 63 nm, about 62 nm,about 61 nm, about 60 nm, about 59 nm, about 58 nm, about 57 nm, about56 nm, about 55 nm, about 54 nm, about 53 nm, about 52 nm, about 51 nm,or about 50 nm.

In some aspects, the grain boundary is enriched with 1 at % Co, 2 at %Co, 3 at % Co, 4 at % Co, 5 at % Co, 6 at % Co, 7 at % Co, 8 at % Co, 9at % Co, 10 at % Co.

One additional advantage of the particles as provided herein accordingto some aspects is an increased atomic lattice order of the nanocrystalsin the material. The combination of nanocrystals with improvedstructural order may produce further enhancement in cycle life andreduction in impedance growth during cycling of cells incorporating theparticles as the or a component of the cathode. Order of nanocrystalsmay be obtained by measuring the relative amount(s) of Ni²⁺ ionsoccupying the Li-site in the LiNiO₂ R-3m layered crystal structure andthe relative z-position of the oxygen atom. Note that Ni²⁺ is meant torepresent all possible elements that are heavier than Li⁺ with largerelectron density that can scatter x-rays that can occupy the Li site(e.g. Ca, Mg, Ni, Co, Al, etc.) Using these parameters, the Ni²⁺ valueof less than or equal to 3.5 at % Ni is considered to have suitableorder to, in combination with crystallite size, product the improvedelectrochemical performance of the materials. It was found that bypreparing grain boundary enriched particles as provided herein that theaverage crystallite size of 105 nm or below could be formed while stillmaintaining the Ni²⁺ relative amount in the Li-site of the crystalstructure of 3.5 at % Ni or below. In some aspects of either a particlewith or without an enriched grain boundary, the relative Ni′ in theLi-sites of the crystal structure is at or below 3.4 at % Ni, optionally3.3 at % Ni, optionally 3.2 at % Ni, optionally 3.1 at % Ni, optionally3.0 at % Ni, optionally 2.9 at % Ni, optionally 2.8 at % Ni, optionally2.7 at % Ni, optionally 2.6 at % Ni, optionally 2.5 at % Ni, optionally2.4 at % Ni, optionally 2.3 at % Ni, optionally 2.2 at % Ni, optionally2.1 at % Ni, optionally 2.0 at % Ni, optionally 1.9 at % Ni, optionally1.8 at % Ni, optionally, 1.7 at % Ni, optionally 1.6 at % Ni, optionally1.5 at % Ni, optionally 1.4 at % Ni. In some aspects, following aprimary calcination as provided herein the Ni′ relative amount in theLi-site of the crystal structure is less than or equal to 1.6 at % Ni,optionally from 1.4 at % Ni to 1.6 at % Ni, or any value or rangetherebetween.

In particular aspects, a particle has an enriched grain boundary,optionally a Co enriched grain boundary where the atomic percentage ofCo in the grain boundary is higher than the atomic percentage of Co inthe nanocrystals. Referring back to FIG. 1 as an exemplary illustration,the grain boundary 41, 42 is between adjacent nanocrystals/grains 40, ison a surface of the nanocrystal/grains 40, and comprises the secondcomposition. As second composition may be as described in U.S. Pat. Nos.9,391,317 and 9,209,455 and may be formed substantially as describedtherein. The second composition optionally has the layered α-NaFeO₂-typestructure, a cubic structure, or a combination thereof. As noted above,a concentration of cobalt in the grain boundaries may be greater than aconcentration of cobalt in the nanocrystals. An aspect in which thegrain boundaries have the layered α-NaFeO₂-type structure isspecifically mentioned.

The second composition of the grain boundaries optionally includeslithiated metal oxides defined by composition Li_(1+x)MO_(2+y), where−0.9≤x≤0.3 and −0.3≤y≤0.3. In some aspects, x is −0.1, optionally 0,optionally 0.1, optionally 0.2, or optionally 0.3. Optionally, x isgreater than or equal to −0.10, −0.09, −0.08, −0.07, −0.06, −0.05,−0.04, −0.03, −0.02, −0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or0.30. In some aspects, y is −0.3, optionally −0.2, optionally −0.1,optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3.Optionally, y is greater than or equal to −0.30, −0.29, −0.28, −0.27,−0.26, −0.25, −0.24, −0.23, −0.22, −0.21, −0.20, −0.19, −0.18, −0.17,−0.16, −0.15, −0.14, −0.13, −0.12, −0.11, −0.10, −0.09, −0.08, −0.07,−0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0.00, 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16,0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28,0.29, or 0.3.

M as provided in the second composition includes Ni. The amount of Ni isoptionally from 10 atomic percent to 99 atomic percent (at %) of M.Optionally, the Ni component of M is greater than or equal to 75 at %.Optionally, the Ni component of M is greater than or equal to 80 at %.Optionally, the Ni component of M is greater than or equal to 85 at %.Optionally, the Ni component of M is greater than or equal to 90 at %.Optionally, the Ni component of M is greater than or equal to 95 at %.Optionally, the Ni component of M is greater than or equal to 75 at %,76 at %, 77 at %, 78 at %, 79 at %, 80 at %, 81 at %, 82 at %, 83 at %,84 at %, 85 at %, 86 at %, 87 at %, 88 at %, 89 at %, 90 at %, 91 at %,92 at %, 93 at %, 94 at %, 95 at %, 96 at %, 98 at %, or 99 at %.

In some aspects, M in a second composition is one or more Nisubstituting elements. The Ni substituting elements are optionallymetals. Optionally, a substituting element may include or be one or moreof Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Zr, Y, Cr, Mo, Fe, V, Si, Ga, or B.In particular aspects, the substituting element may include Mg, Co, Al,or a combination thereof.

A substitution element of the second composition may be present in anamount of about 1 to about 90 at %, specifically about 5 to about 80 at%, more specifically about 10 to about 70 at % of the first composition.Optionally, the additional element may be present in an amount of about1 to about 20 at %, specifically about 2 to about 18 at %, morespecifically about 4 to about 16 at %, of the first composition.

The shape of the grain boundary is defined by the shape of the grainwhich may represent one or more fused nanocrystal(s) adjacent the grainboundary. The shape of the grain boundary may approximate a geometricshape. The grain boundary may have a rectilinear shape, and when viewedin cross-section the grain boundary may be rectilinear. The grainboundary may be square, hexagonal, rectangular, triangular, or acombination thereof.

A direction of a surface of the grain boundary corresponds to adirection of a surface of the adjacent nanocrystal. Also, as shown inFIG. 1 , the surface of the grain boundary and the surface of thenanocrystal may have any of a variety of orientations relative to anouter surface of the particle. Thus, the direction of the surface of thenanocrystal and the direction of the surface of the grain boundary maybe parallel and be different than a direction of a nearest outer surfaceof the secondary particle. In some aspects, a direction of a tangent ofthe nearest outer surface of the particle is different than thedirection of the surface of the grain boundary and the direction of thesurface of the adjacent particle.

As is also shown in FIG. 1 , the grain boundaries may intersect to forman angle therebetween. In some aspects, disposed on adjacent faces of ananocrystal/grain 40 is a first grain boundary 41 and second grainboundary 42. The first grain boundary 41 and the second grain boundary42 intersect at an angle E. The angle E may be defined by the shape ofthe nanocrystal on which the first grain boundary 41 and the secondgrain boundary 42 are disposed. Generally, a shape of a nanocrystal isinfluenced by a crystal structure of the nanocrystal. While not wantingto be bound by theory, it is understood that because the crystalstructure of the first composition governs the shape of the nanocrystal,the angle between the first and second grain boundaries 41, 42 isinfluenced by the crystal structure of the first composition. The firstand second grain boundaries 41, 42 may intersect at any angle,specifically an angle of about 10 to about 170 degrees, specificallyabout 20 to about 160 degrees, more specifically about 30 to about 150degrees, so long as the angle is consistent with the crystal structureof the first composition, which optionally has the layered α-NaFeO₂-typestructure.

The particle may be prepared by synthesizing a green body from at leasttwo components, optionally in powder form. At least two components mayinclude micronized (or non-micronized) lithium hydroxide or its hydrateand a precursor hydroxide(s) comprising nickel, and or one or more otherelements. It is appreciated that the final overall composition (althoughnot necessarily distribution) of the elements in the final particle maybe adjusted by increasing or decreasing the relative amounts of theprecursor materials in the formation of the green body. In some aspects,the lithium hydroxide or its hydrate are micronized. The two or morepowders forming the green body may be combined and shaken on a paintshaker to thoroughly mix the precursors. The green body is then calcinedwith a controlled air atmosphere to a maximum temperature whereby waterand CO₂ are minimized. Calcining is optionally preformed following aheating curve to provide the desired average crystallite size. Thecalcined product may then be processed to form a free-flowing powder.

In some aspects, the precursor hydroxide may be a mixed metal hydroxide.In some aspects, the mixed metal hydroxide may include a metalcomposition of Ni, Co, and Mg. Optionally, the mixed metal hydroxideincludes as a metal component 80-100 at % Ni, 0-15 at % Co, and 0-5 at %Mg. Optionally, the metals of the mixed metal hydroxide is 92 at % Niand 8 at % Co. Optionally, the metals of the mixed metal hydroxide is 90at % Ni, 8 at % Co, and 2 at % Mg. Optionally, the metals of the mixedmetal hydroxide is 89 at % Ni, 8 at % Co, 3 at % Mg. Optionally, themetals of the mixed metal hydroxide is 91 at % Ni, 8 at % Co, and 1 at %Mg. Optionally, the metal of the mixed metal hydroxide is 100 at % Ni.For example, precursor hydroxide may be made by a precursor supplier,such as Hunan Brunp Recycling Technology Co. Ltd., using standardmethods for preparing nickel-hydroxide based materials.

It was found that by reducing the maximum temperature of a firstcalcination a particulate material with relatively small crystal (i.e.,nanocrystals) could be prepared. As such, in a first calcination, amaximum temperature may be less than 700 degrees Celsius. Optionally,the maximum temperature may be about 680 degrees Celsius or less.Optionally, the maximum temperature may be about 660 degrees Celsius orless. Optionally, the maximum temperature may be about 640 degreesCelsius or less. In yet other aspects, the maximum temperature may beless than about 700 degrees Celsius, about 695 degrees Celsius, about690 degrees Celsius, about 685 degrees Celsius, about 680 degreesCelsius, about 675 degrees Celsius, about 670 degrees Celsius, about 665degree Celsius, about 660 degrees Celsius, about 655 degrees Celsius,about 650 degrees Celsius, about 645 degrees Celsius, or about 640degrees Celsius. The dwell time at the maximum temperature is optionallyless than 10 hours. Optionally, the dwell time at the maximumtemperature is less than or equal to 8 hours; optionally less than orequal to 7 hours; optionally less than or equal to 6 hours; optionallyless than or equal to 5 hours; optionally less than or equal to 4 hours;optionally less than or equal to 3 hours; optionally less than or equalto 2 hours.

It was found that in some aspects reducing the temperature below aminimum temperature reduced the electrochemical improvements observed.As such, for a first calcination a maximum temperature in some aspectsis at least about 640 degrees Celsius, optionally about 645 degreesCelsius, optionally about 650 degrees Celsius. In some aspects, amaximum temperature must be reached and such maximum temperature isoptionally from about 640 degrees Celsius to about 695 degrees Celsius,optionally from about 645 degrees Celsius to about 695 degrees Celsius,optionally from about 650 degrees Celsius to about 695 degrees Celsius,optionally from about 655 degrees Celsius to about 695 degrees Celsius,optionally from about 645 degrees Celsius to about 680 degrees Celsius,optionally from about 650 degrees Celsius to about 680 degrees Celsius,optionally from about 655 degrees Celsius to about 680 degrees Celsius,optionally from about 660 degrees Celsius to about 680 degrees Celsius.

In some aspects, the heating curve of the first calcination processfollows a two ramp/dwell process followed by natural cooling to about130 degrees Celsius whereupon the calcined material is subsequentlyprocessed. As an illustrative aspect, the first ramp/dwell may be fromambient (e.g. about 25 degrees Celsius) to 450 degrees Celsius at a rateof 5 degree Celsius per minute with a 2 hour hold at 450 degreesCelsius. Subsequently, the second ramp/dwell may be from 450 degreesCelsius to a maximum temperature at a rate of 2 degree Celsius perminute with a 6 hour hold at the maximum temperature.

After calcination, subsequent processing may include breaking up thecalcined material with a mortar and pestle so that the resulting powderpasses through a desired sieve, optionally a #35 sieve. The powder isoptionally then jar milled in a 1 gallon jar with a 2 cm drum YSZ mediafor optionally 5 minutes or an adequate time such that the material maypasses through optionally a #270 sieve.

In some aspects, the milled product may be coated, optionally in amethod so as to result in enriched grain boundaries following a secondcalcination. A process of coating to enrich grain boundaries within aprimary particle may be performed by methods or using compositions asillustrated in U.S. Pat. Nos. 9,391,317 and 9,209,455. The coating mayoptionally be applied by suspending the milled product in an aqueousslurry comprising an enrichment element, optionally cobalt, and lithiumnitrate optionally at a temperature of 60 degrees Celsius. The slurrymay then be spray dried to form a free-flowing powder which is thensubjected to a second calcination optionally with a heating curvefollowing a two ramp/dwell process. The first two ramp/dwell temperatureprofile may be from ambient (about 25 degree Celsius) to 450 degreeCelsius and at a rate of 5 degree Celsius per minute with a 1 hour holdat 450 degrees Celsius. Subsequently, the second ramp/dwell may be from450 degrees Celsius to a maximum temperature at a rate of 2 degreeCelsius per minute with a 2 hour hold at the maximum temperature. Insome aspects, the maximum temperature is about 700 degrees Celsius. Inother aspects, the maximum temperature is about 725 degrees Celsius.

By combining a first calcination with a maximum temperature as describedabove with a coating by second calcination also as described above itwas found that average crystallite size of 105 nm (XRD measurement) orless could be maintained while simultaneously maintaining the samesequential ordering of the materials with an Ni²⁺ of 3.5 at % Ni orlower. Such a combination was found to result in additional cycle lifeand reduction in impedance growth significantly improving theelectrochemical performance of the material. As such, it is appreciatedthat in some aspects, a particle includes a plurality of nanocrystalswith a first composition including polycrystalline layered-structurelithiated metal oxides defined by composition Li_(1+x)MO_(2+y) where−0.1≤x≤0.3 and −0.3≤y≤0.3. In some aspects x is −0.1, optionally 0,optionally 0.1, optionally 0.2, or optionally 0.3. Optionally x isgreater than or equal to −0.10, −0.09, −0.08, −0.07, −0.06, −0.05,−0.04, −0.03, −0.02, −0.01, 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06,0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18,0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, or0.30. In some aspects, y is −0.3, optionally −0.2, optionally −0.1,optionally 0, optionally 0.1, optionally 0.2, or optionally 0.3.Optionally, y is greater than or equal to −0.30, −0.29, −0.28, −0.27,−0.26, −0.25, −0.24, −0.23, −0.22, −0.21, −0.20, −0.19, −0.18, −0.17,−0.16, −0.15, −0.14, −0.13, −0.12, −0.11, −0.10, −0.09, −0.08, −0.07,−0.06, −0.05, −0.04, −0.03, −0.02, −0.01, 0.00, 0.01, 0.02, 0.03, 0.04,0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16,0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28,0.29, or 0.3. The nanocrystals have an amount of Ni in the M element of10 atomic percent to 99 atomic percent (at %) of the particle.Optionally, the Ni component of M is greater than or equal to 75 at %.Optionally, the Ni component of M is greater than or equal to 80 at %.Optionally, the Ni component of M is greater than or equal to 85 at %.Optionally, the Ni component of M is greater than or equal to 90 at %.Optionally, the Ni component of M is greater than or equal to 95 at %.Optionally, the Ni component of M is greater than or equal to 75 at %,76 at %, 77 at %, 78 at %, 79 at %, 80 at %, 81 at %, 82 at %, 83 at %,84 at %, 85 at %, 86 at %, 87 at %, 88 at %, 89 at %, 90 at %, 91 at %,92 at %, 93 at %, 94 at %, 95 at %, 96 at %, 98 at %, or 99 at %. The Mcomponent may include one or more additional elements. The additionalelements are optionally metals. Optionally, an additional element mayinclude or be one or more of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Zr, Y, Cr,Mo, Fe, V, Si, Ga, or B. In particular aspects, the additional elementmay include Mg, Co, Al, or a combination thereof. Optionally, theadditional element may be Mg, Al, V, Ti, B, Zr, or Mn, or a combinationthereof. Optionally, the additional element consists of Mg, Al, V, Ti,B, Zr, or Mn. In some aspects, the additional element is Mn or Mg, orboth Mn and Mg. The additional element of the first composition may bepresent in an amount of about 1 to about 90 at %, specifically about 5to about 80 at %, more specifically about 10 to about 70 at % of thefirst composition. Optionally, the additional element may be present inan amount of about 1 to about 20 at %, specifically about 2 to about 18at %, more specifically about 4 to about 16 at %, of the firstcomposition. In some illustrative examples, M is about 75-99 at % Ni,3-15 at % Co, 0-15 at % Mn, and 0-10 at % additional elements. Also, theaverage crystallite size of the nanocrystals (as determined by X-raydiffraction methods described hereinabove) is less than or equal toabout 105 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 100 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 95 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 90 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 85 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 80 nm. Optionally, theaverage crystallite size of the nanocrystals is less than or equal toabout 75 nm. Optionally, the average crystallite size of thenanocrystals is less than or equal to about 70 nm. In some aspects, theaverage crystallite size of the nanocrystals is greater than or equal to70 nm to less than or equal to about 105 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about70 nm to less than or equal to about 100 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about70 nm to less than or equal to about 105 nm. Optionally, the averagecrystallite size of the nanocrystals is greater than or equal to about75 nm to less than or equal to about 100 nm. In other aspects, theaverage crystallite size of the nanocrystals is less than or equal toabout 105 nm, about 104 nm, about 103 nm, about 102 nm, about 101 nm,about 100 nm, about 99 nm, about 98 nm, about 97 nm, about 96 nm, about95 nm, about 94 nm, about 93 nm, about 92 nm, about 91 nm, about 90 nm,about 89 nm, about 88 nm, about 87 nm, about 86 nm, about 85 nm, about84 nm, about 83 nm, about 82 nm, about 81 nm, about 80 nm, about 79 nm,about 78 nm, about 77 nm, about 76 nm, about 75 nm, about 74 nm, about73 nm, about 72 nm, about 71 nm, or about 70 nm.

Optionally the particles further have atomic lattice orderednanocrystals illustrated by the relative amount(s) of Ni²⁺ ionsoccupying the Li-site in the LiNiO₂ R-3m layered crystal structurewhereby the Ni²⁺ value of less than or equal to 3.5%, optionally lessthan 3.2 at % Ni, optionally equal to or less than 2.5%. The atomic % Niin the M element is optionally 75 at % to 99 at %, optionally 80 at % to95 at %.

Optionally an outer layer illustrated at 30 in FIG. 1 , such as apassivation layer or a protective layer, may be disposed on an outersurface of the particle. The outer layer may fully or partially coverthe secondary particle. The layer may be amorphous or crystalline. Thelayer may comprise an oxide, a phosphate, a pyrophosphate, afluorophosphate, a carbonate, a fluoride, an oxyfluoride, or acombination thereof, of an element such as Zr, Al, Ti, Al, B, Li, or Si,or a combination thereof. In some aspects the outer layer comprises aborate, an aluminate, a silicate, a fluoroaluminate, or a combinationthereof. Optionally, the outer layer comprises a carbonate. Optionally,the outer layer comprises ZrO₂, Al₂O₃, TiO₂, AlPO₄, AlF₃, B₂O₃, SiO2,Li₂O, Li₂CO₃, or a combination thereof. Optionally, an outer layerincludes or is AlPO₄ or Li₂CO₃. The layer may be disposed by any processor technique that does not adversely affect the desirable properties ofthe particle. Representative methods include spray coating and immersioncoating, for example.

Also provided are electrodes that include as a component of or the soleelectrochemically active material a particle as described herein. Aparticle as provided herein is optionally included as an activecomponent of a cathode. A cathode optionally includes a particledisclosed above as an active material, and may further include aconductive agent and/or a binder. The conductive agent may comprise anyconductive agent that provides suitable properties and may be amorphous,crystalline, or a combination thereof. The conductive agent may includea carbon black, such as acetylene black or lamp black, a mesocarbon,graphite, carbon fiber, carbon nanotubes such as single wall carbonnanotubes or multi-wall carbon nanotubes, or a combination thereof. Thebinder may be any binder that provides suitable properties and mayinclude polyvinylidene fluoride, a copolymer of polyvinylidene fluorideand hexafluoropropylene, poly(vinyl acetate), poly(vinylbutyral-co-vinyl alcohol-co vinyl acetate),poly(methylmethacrylate-co-ethyl acrylate), polyacrylonitrile, polyvinylchloride-co-vinyl acetate, polyvinyl alcohol,poly(l-vinylpyrrolidone-co-vinyl acetate), cellulose acetate,polyvinylpyrrolidone, polyacrylate, polymethacrylate, polyolefin,polyurethane, polyvinyl ether, acrylonitrile-butadiene rubber,styrene-butadiene rubber, acrylonitrile-butadiene-styrene, tri-blockpolymer of sulfonated styrene/ethylene-butylene/styrene, polyethyleneoxide, or a combination thereof, for example.

The cathode may be manufactured by combining the particle as describedherein, the conductive agent, and the binder in a suitable ratio, e.g.,about 80 to about 98 weight percent of the particle, about 2 to about 20weight percent of the conductive agent, and about 2 to about 10 weightpercent of the binder, based on a total weight of the particle, theconductive agent, and the binder combined. The particle, the conductiveagent, and the binder may be suspended in a suitable solvent, such asN-methylpyrrolidinone, and disposed on a suitable substrate, such asaluminum foil, and dried in air. It is noted that the substrate and thesolvent are presented for illustrative purposes alone. Other suitablesubstrates and solvents may be used or combined to form a cathode.

In some aspects, a cathode comprising a polycrystalline material havingan average crystallite size of the nanocrystals that is less than orequal to about 85 nm or less than or equal to 105 nm depending on thepresence or absence of enriched grain boundaries may exhibit anelectrochemical discharge capacity of greater than 205 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V. In yet another aspect, the cathode may exhibit anelectrochemical discharge capacity of greater than 200 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V. In yet another aspect, the cathode may exhibit anelectrochemical discharge capacity of greater than 190 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V. In yet another aspect, the cathode may exhibit anelectrochemical discharge capacity of greater than 180 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V. In yet another aspect, the cathode may exhibit anelectrochemical discharge capacity of greater than 175 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V. In yet another aspect, the cathode may exhibit anelectrochemical discharge capacity of greater than 170 mAh/g at a C/20rate when the electrode is charged to 4.3 V versus L-metal anddischarged to 3.0 V.

A cathode as proved above when cycled with a lithium foil anode, apolyolefin separator and an electrolyte of 1 M LiPF₆ in 1/1/1 (vol.)EC/DMC/EMC with 1 wt. % VC in a 2025 coin cell optionally demonstrates asignificantly reduced impedance growth. One measure of impedance growthis illustrated by charging the cell at 1 C rate to 4.2V (CCCV) anddischarging it to 2.7 V. The time spent at constant voltage during thischaracterization step may be used as a measure of impedance. Theimpedance measurement plotted against cycle number results in a curvewith a defined slope. The impedance slope is lower when active particlematerial has a crystallite size or order as described herein relative toparticles with a larger crystallite size (e.g. greater than 85 nm). Insome aspects, the impedance slope is 0.025 or less, optionally 0.024 orless, optionally 0.023 or less, optionally 0.022 or less, optionally0.021 or less, optionally 0.020 or less, optionally 0.019 or less,optionally 0.018 or less, optionally 0.017 or less, optionally 0.016 orless, optionally 0.015 or less.

Also disclosed is a battery comprising the cathode. The battery may be alithium-ion battery, a lithium-polymer battery, or a lithium battery,for example. The battery may include a cathode, an anode, and aseparator interposed between the cathode and the anode. The separatormay be a microporous membrane, and may include a porous film includingpolypropylene, polyethylene, or a combination thereof, or may be a wovenor non-woven material such a glass-fiber mat. The anode may include acoating on a current collector. The coating may include a suitablecarbon, such as graphite, coke, a hard carbon, or a mesocarbon such as amesocarbon microbead, for example. The current collector may be copperfoil, for example.

The battery also includes an electrolyte that may contact the positiveelectrode (cathode), the negative electrode (anode), and the separator.The electrolyte may include an organic solvent and a lithium salt. Theorganic solvent may be a linear or cyclic carbonate. Representativeorganic solvents include ethylene carbonate, propylene carbonate,butylene carbonate, trifluoropropylene carbonate, γ-butyrolactone,sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methylpropionate,ethylpropionate, dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, dipropyl carbonate, methylpropyl carbonate, propane sultone,or a combination thereof. In another aspect the electrolyte is a polymerelectrolyte.

Representative lithium salts useful in an electrolyte include but arenot limited to LiPF₆, LiBF₄, LiAsF₆, LiClO₄, LiCF₃SO₃, Li(CF₃SO₂)₂N,LiN(SO₂C₂F₅)₂, LiSbF₆, LiC(CF₃SO₂)₃, LiC₄F₉SO₃, and LiAlCl₄. The lithiumsalt may be dissolved in the organic solvent. A combination comprisingat least one of the foregoing can be used. The concentration of thelithium salt can be 0.1 to 2.0M in the electrolyte.

The battery may have any suitable configuration or shape, and may becylindrical or prismatic.

Various aspects of the present disclosure are illustrated by thefollowing non-limiting examples. The examples are for illustrativepurposes and are not a limitation on any practice of the presentinvention. It will be understood that variations and modifications canbe made without departing from the spirit and scope of the invention.

EXAMPLES

The average crystallite size of nanocrystals may be determined usingpowder X-ray diffraction patterns collected from a continuous scanbetween 12 and 120 degrees in 2-theta at 0.75 degrees/min using anautomated Shimadzu XRD-6000 diffractometer with a Cu X-ray tube. Atomicstructure analysis and crystallite size analysis may be performed usingRietveld refinement technique implemented in MDI Jade 7 program oranother equivalent program. Procedures for atomic structure refinementsare evident to those skilled in the art. Using these refinements, the a-and c-lattice parameters for the LiNiO₂ R-3m layered crystal structureand relative amount of Ni′ ions occupying the Li-site and the relativez-position of the oxygen atom may be obtained. Background curve of a3rd-order polynomial and the Pseudo-Voigt profile shape function may beused for peak fitting. Peak broadening may be fit for both crystallitesize and strain or for crystallite size only in MDI Jade. Crystallitesize-fitting only (without strain) is used for determining the averageprimary crystallite size for materials synthesized under differentreaction conditions. Instrumental FWHM calibration curve can be obtainedby profile fitting diffraction pattern of a calibration standard, such aNIST SRM 640 Si or SRM 660 LiB₆ powders.

Example 1: Two Samples of Polycrystalline 2D α-NaFeO₂-Type LayeredStructure Particles with Differing Crystallite Sizes

Two electrochemically active polycrystalline 2D α-NaFeO₂-type layeredstructure particles having differing crystallite sizes with high nickelin the cathode material were prepared. The two prepared samples ofpolycrystalline 2D α-NaFeO₂-type layered structure had an overallcompositionLi_((0.98))Mg_((0.02))Ni_((0.881))Co_((0.115))Al_((0.004))O_((2.0)). Onesample was made by calcining the green body at 700° C. and the secondcalcined at 680° C. The two materials were made from the same green bodyformulation comprising 80.21 g of micronized LiOH and 288.2 g ofprecursor hydroxide. The precursor hydroxide contained an atomicallymixed combination of 90.2 at % Ni, 7.8 at % Co, and 2.0 at % Mg.

Two portions of the green body blend were then calcined with differentheating curves under a stream of CO₂-free, dry air. The “hightemperature” used to make the “large crystallite” ramped from 25° C. to450° C. at 5° C./min with a soak time of 2 hours followed by a secondramp at 2° C./min to a maximum temperature of 700° C. and a soak time of6 hours. The “low temperature” used to make the “small crystallite size”(representing a nanocrystal) ramped from 25° C. to 450° C. at 5° C./minwith a soak time of 2 hours followed by a second ramp at 2° C./min to amaximum temperature of 680° C. and a soak time of 6 hours.

Each material was then permitted to naturally cool to 100° C. Thecalcined materials was first individually ground in a mortar and pestleand then milled in a jar mill. The “large crystallite” product wasmilled for 10 minutes while the “small crystallite size” material wasmilled for 5 minutes.

The properties of the two materials are summarized in Table 1. The twomaterials were subjected to a suite of tests to identify averageoxidation state, residual lithium hydroxide, and ion mixing in thelayered crystals. The synthesized materials were substantially identicalfrom the typical metrics commonly used for characterizing cathodepowders (oxidation state, residual lithium hydroxide, and cationmixing). The only significant difference was in the average crystallite.

TABLE 1 Properties of the large crystallite and small crystallite(nanocrystal) materials. Large Small Crystallite Crystallite Size SizeTest Material Material Description Average Oxidation 2.98+ 2.99+ Redoxtitration State of the transition metals Residual Lithium 0.08% 0.06%Extraction and titration Hydroxide Result is weight % (wt %) Ion Mixing1.6% 1.6% Rietveld Refinement of (% of Li-sites X-Ray Diffractionoccupied by ions measurements of the with 2⁺ oxidation powder state)Average Crystallite 87 65 Determined from peak Size (nm) broadening ofX-Ray Diffraction measurements of the powder (fitted for crystallitesize only, no strain)

Prior to forming electrodes, the synthesized powders were coated toenrich grain boundaries with a mixture of cobalt and aluminum,sufficient to make the aforementioned formulation, using an identicalprocess. After coating both materials, the materials were subjected toanother heat treatment under flowing CO₂-free, dry air. The heatingcurve used for this treatment was a ramp from 25° C. to 450° C. at 5°C./min with a soak time of 1 hour followed by a second ramp at 2° C./minto 700° C. and a soak time of 2 hours. The materials were then naturallycooled to 100° C. and were milled for 5 minutes in ajar mill. Theresulting parameters of the grain boundary enriched materials areillustrated in Table 2.

TABLE 2 Fitted XRD parameters for coated materials with 4 at % Coenrichment at the grain boundary. XS (nm) Average Crystallite sizefitted Material Synthetic Temp a (Å) c (Å) z_(o) Ni²⁺ without strainLarge Crystallite Size 2.873 14.186 0.241 1.7% 109 Material SmallCrystallite Size 2.873 14.186 0.241 2.0% 77.8 Material

The materials were each blended with PVDF binder and conductive carbonin a slurry of NMP solvent and coated onto an aluminum foil currentcollector. Cathode electrodes were then punched out of the foil andcombined with MCMB graphite anodes, porous polypropylene separators andcarbonate based electrolytes in a “full” coin cell format forelectrochemical cycle life testing. The cathode electrodes were alsocombined with lithium metal anodes, porous polypropylene separators andcarbonate based electrolytes in a “half” coin cell format forelectrochemical discharge capacity testing.

The results of the half-cell testing are shown in Table 3, below. A highdischarge capacity of greater than 205 mAh/g at C/20 is achieved forboth samples.

TABLE 3 Electrochemical Discharge Capacity Testing Results C/20 C/20 1 C5 C Charge Discharge Discharge Discharge Cathode Type mAh/g mAh/gEfficiency mAh/g mAh/g Large Crystal 230 212 92% 189 178 CathodeNanocrystal 231 214 92% 189 177 Cathode

The full cells were cycled through a series of charge and dischargecycles at room temperature initially and then at 45° C. The results forthe tests at 45° C. between cycles 100 and 200 are shown in the FIGS. 2and 3 , below. FIG. 2 is a graph of the discharge capacity fade betweencycles 100 and 200 at 45° C. for duplicate cells containing cathodematerials with large crystals or nanocrystals. FIG. 3 illustrates theincrease in dimensionless impedance value for duplicate cells containingcathode materials with large crystallite size or small crystallite size(e.g., nanocrystals) corresponding to the cycling data shown in FIG. 2 .The impedance value was measured every 20 charge/discharge cycles. Notethe improvement in the initially high discharge capacity and initiallylow impedance for the materials with the small nanocrystals. Morespecifically, a residual capacity of 85% or greater is achieved at cycle200. Further, the capacity retention during cycling is better and therate of impedance growth is lower for the material with smallnanocrystals.

Example 2: Four Cathode Powders withLi_((0.98))Mg_((0.02))Ni_((0.863))Co_((0.131))Al_((0.006))O₍₂₎Formulation Differing in Crystallite Size

Four electrochemically active polycrystalline 2D α-NaFeO₂-type layeredstructure particles having differing crystallite sizes with high nickelwere prepared. The four prepared samples of polycrystalline 2Dα-NaFeO₂-type layered structure each had an overall compositionLi_((0.98))Mg_((0.02))Ni_((0.863))Co_((0.131))Al_((0.006))O_((2.0)).

A green body blend was synthesized from two powder componentssubstantially as in Example 1. The powders were combined in a ½ gallonHDPE bottle and shaken on a paint shaker for 10 minutes to producethorough mixing. This green body blend was then calcined with acontrolled air atmosphere whereby water and CO₂ were minimized.Calcination formed a sintered ceramic product which was subsequentlyprocessed to form a free-flowing powder.

The two powders combined into the green body were micronized lithiumhydroxide and a mixed metal hydroxide. The lithium hydroxide wasmicronized by shaking 250 g with 1200 g of yttrium stabilized zirconia(YSZ) media (spherical, ¼″ dia) in a ½ gallon HDPE bottle for 45minutes. The mixed metal hydroxide had a metal composition that was 90at % Ni, 8 at % Co and 2 at % Mg. This was made by a precursor supplier,Hunan Brunp Recycling Technology Co. Ltd., using standard methods forpreparing nickel-hydroxide based materials.

The first calcination heating curve followed two ramp/dwells followed bynatural cooling to 130° C. whereupon it was subsequently processed. Thefirst ramp/dwell was from ambient to 450° C. at 5° C./min with a 2 hourhold while the second was from 450° C. to a maximum temperature at 2°C./min with a 6 hour hold. Four sets of materials were calcined withfour different maximum temperatures of 640° C., 660° C., 680° C. and700° C.

For the materials made at the three lowest temperatures (i.e., 640° C.,660° C., and 680° C.), a single green body blend was made from 252 g oflithium hydroxide and 961 g of mixed metal hydroxide powder. This wasthen split into thirds and each third placed into one of three cruciblesfor calcination. After calcination, subsequent processing comprisedinitially breaking up the sintered cake with a mortar and pestle so thatthe resulting powder passed through a #35 sieve. The powder was then jarmilled in a 1 gallon jar with 2 cm drum YSZ media for 5 minutes andsieved through a #270 sieve.

The material calcined at 700° C., comprised a green body blend made from252 g of lithium hydroxide and 941 g of mixed metal hydroxide. Thisblend was calcined in 9 crucibles evenly spread across three identicallyprogrammed furnaces. After calcination, subsequent processing comprisedinitially breaking up the sintered cake with a mortar and pestle so thatthe resulting powder passed through a #35 sieve. The powder was then jarmilled in a 1 gallon jar with 2 cm drum YSZ media for 10 minutes andsieved through a #270 sieve.

Prior to forming electrodes, the synthesized powders were coated with amixture of cobalt and aluminum, sufficient to make the aforementionedformulation, using an identical process. After coating both materials,the materials were subjected to another heat treatment under flowingCO₂-free, dry air. The heating curve used for this treatment was a rampfrom 25° C. to 450° C. at 5° C./min with a soak time of 1 hour followedby a second ramp at 2° C./min to 700° C. and a soak time of 2 hours. Thematerials were then naturally cooled to 100° C. and were milled for 5minutes in ajar mill.

Electrode coatings were made for each of the four cathode powders byblending the cathode powder with PVdF (Kureha KF-1120) and carbon (Denkablack) in N-methylpyrrolidinone to form a slurry, and then coating eachslurry onto an aluminum foil current collector. Cathodes were thenpunched from the coated aluminum foil.

Half cells were assembled by combination of the cathode with lithiumfoil, a polyolefin separator (Celgard 2500) and an electrolyte of 1 MLiPF₆ in 1/1/1 (vol.) EC/DMC/EMC with 1 wt. % VC (Kishida Chemical) in a2025 coin cell. The capacity of each cell was determined by calculationfrom the electrode weight, assuming a capacity of 200 mAh/g cathodematerial. The cells were then charged to 4.3 V at C/20, and dischargedat rates from C/20 to 5 C. With respect to charge or discharge rates, Crefers to the C-rate, which is the rate to charge or discharge the cellin one hour. The results of the half-cell analysis are shown in Table 4.

TABLE 4 Half Cell results Discharge Capacity Cathode Synthetic (mAh/g)Ratio of Temperature C/20 C/5 2 C 2 C to C/5 700° C. 211 203 184 90.9%680° C. 210 199 181 91.0% 660° C. 206 194 177 91.2% 640° C. 206 194 17690.7%

Full cells were assembled by combination of the cathode with a graphiticanode, a polyolefin separator (Celgard 2500) and an electrolyte of 1 MLiPF₆ in 1/1/1 (vol.) EC/DMC/EMC with 1 wt. % VC (Kishida Chemical) in a2025 coin cell the cathode half of which had been coated with aluminum.The capacity of each cell was determined by calculation from theelectrode weight, assuming a capacity of 200 mAh/g cathode material. Theanode was matched to the cathode weight such that the anode capacityexceeded the cathode by a factor ranging from 1.27 to 1.30.

The graphitic anode coating used MCMB 1028 active materials and was madeby blending the active with PVdF (Kureha KF-1120) and carbon (Denkablack) in N-methylpyrrolidinone to form a slurry, and then coating eachslurry onto a copper foil current collector. Anodes were then punchedfrom the coated copper foil.

The full coin cells were then formed at C/5 at 25° C. and cycled at 45°C. with a charging current of 1.5 C to 4.25 V and a discharging currentthat ended at 1 C at 2.7 V. Every 20 cycles, the capacity and impedancewere characterized by charging the cell at 1 C rate to 4.2V (CCCV) anddischarging it to 2.7 V. The time spent at constant voltage (i.e., CVstep) during this characterization step was used as a measure of theimpedance.

TABLE 5 XRD Crystallite Size and Impedance Factor Crystallite SizeImpedance Calc Temp Final Product Factor (deg. C.) (nm) Slope 700 82.40.028 680 71.8 0.019 660 63.1 0.018 640 52.3 0.024

The crystallite sizes were determined using powder X-ray diffractionpatterns collected using a continuous scan between 12 and 120 degrees in2-theta at 0.75 degrees/min using an automated Shimadzu XRD-6000diffractometer with a Cu X-ray tube. Atomic structure analysis andcrystallite size analyses were performed using Rietveld refinementtechnique implemented in MDI Jade 7 program. Procedures for atomicstructure refinements are evident to those skilled in the art. Usingthese refinements, the a- and c-lattice parameters for the LiNiO₂ R-3mlayered crystal structure and the relative amount of Ni²⁺ ions occupyingthe Li-site and the relative z-position of the oxygen atom wereobtained. Background curve of a 3rd-order polynomial and thePseudo-Voigt profile shape function was used for peak fitting. Peakbroadening was fit for crystallite size only (with no strain).Instrumental FWHM calibration curve was obtained by profile fittingdiffraction pattern of a NIST 640c Si calibration standard. Crystallitesize-fitting without strain is used for determining the average primarycrystallite size for materials synthesized under different reactionconditions. Results are illustrated in Table 6.

TABLE 6 XRD Parameters for Materials made at a range of temperaturesbefore coating. XS (nm) Material Crystallite Synthetic size fitted Tempa (Å) c (Å) z_(o) Ni²⁺ without strain 700° C. 2.873 14.193 0.241 1.7%87.0 680° C. 2.873 14.193 0.241 1.5% 68.5 660° C. 2.873 14.193 0.2411.8% 56.6 640° C. 2.872 14.186 0.241 2.3% 38.4

After the coating is applied and the materials are recalcined for ashort period, some crystal growth is observed by XRD for most materials.For 700° C. calcination the apparent slight decrease in crystallite sizeis observed as a result of slight lattice parameter distortion caused bygrain boundary enrichment. However, the same sequential ordering in sizecreated in the original calcination is maintained. Also the disorder hasbeen maintained at low levels with Ni′ value remaining below 3.5 at %Ni.

TABLE 7 XRD Parameters for Materials made at a range of temperaturesafter coating with 6 at % Co enrichment. XS (nm) Material CrystalliteSynthetic size fitted Temp a (Å) c (Å) z_(o) Ni²⁺ without strain 700° C.2.872 14.186 0.241 2.4% 82.4 680° C. 2.873 14.194 0.241 2.5% 71.8 660°C. 2.874 14.192 0.241 3.1% 63.1 640° C. 2.873 14.189 0.241 2.5% 52.3

Referring now to FIG. 4 , a graph depicting impedance values betweencycles 100 and 200 for two samples of each of the four cathode powderswherein the first calcination was performed at temperatures of 700degrees Celsius or less is depicted. As shown, crystallite sizedecreases as the maximum calcination temperature decreases.Additionally, the impedance slope, quantified in Table 5, also decreaseswith calcination temperature, notwithstanding calcination at 640 degreeCelsius where the impedance slope increases. A calcination maximumtemperature of less than 700 degree Celsius and greater than 640 degreeCelsius achieves a low rate of impedance growth during charge/dischargecycling of the battery and high discharge capacity as depicted in Table4.

It should now be understood that aspects described herein may bedirected to compositions and methods of manufacturing of positiveelectrode (cathode) active materials for Li-ion batteries with smallnanocrystals in order to reduce the rate of impedance growth duringcharge/discharge cycling of the battery. The described compositions andmethods of manufacturing include active polycrystalline particlesforming positive electrodes that achieve materials with an averagecrystallite size of 85 nm or less (or 105 nm or less for grain boundaryenriched particles) in high-nickel formulations and also have highdischarge capacity that is greater than or equal to 205 mAh/g at C/20.The provided compositions and methods of manufacturing for the positiveelectrode (cathode) active materials exhibit dramatically enhancedelectrochemical performance and stability whereby lithium isde-intercalated and re-intercalating into the crystal lattice.

The foregoing description is illustrative of particular aspects of theinvention, but is not meant to be a limitation upon the practicethereof. The following claims, including all equivalents thereof, areintended to define the scope of the invention.

We claim:
 1. An electrochemically active polycrystalline particlecomprising: a plurality of nanocrystals, the plurality of nanocrystalscomprising a first composition defined by Li_(1+x)MO_(2+y), wherein−0.1≤x≤0.3,−0.3y≤0.3, and wherein M comprises nickel at greater than or equal to 10atomic percent; and said plurality of nanocrystals having an averagecrystallite size of less than or equal to 105 nanometers as measured byX-ray diffraction, a grain boundary between adjacent nanocrystals ofsaid plurality of nanocrystals and comprising a second compositionwherein a concentration of cobalt in said grain boundary is greater thana concentration of cobalt in said nanocrystals.
 2. The particle of claim1, wherein said size of said plurality of nanocrystals have an averagecrystallite size greater than or equal to 50 nanometers to less than orequal to 85 nanometers.
 3. The particle of claim 1, wherein said size ofsaid plurality of nanocrystals is less than or equal to 80 nanometers.4. The particle of claim 1, wherein said size of said plurality ofnanocrystals is less than or equal to 70 nanometers.
 5. The particle ofclaim 1 wherein M further comprises one or more elements selected fromthe group consisting of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Zr, Y, Cr, Mo,Fe, V, Si, Ga and B.
 6. The particle of claim 1, wherein M comprisesnickel at an atomic percent greater than or equal to 80%.
 7. Theparticle of claim 1, further comprising an outer coating on a surface ofthe particle, the outer coating comprising: an oxide of one or moreelements selected from Al, Zr, Y, Co, Ni, Mg, and Li; a fluoridecomprising one or more elements selected from Al, Zr, and Li; acarbonate comprising one or more elements selected from Al, Co, Ni, Mn,and Li; or a phosphate comprising one or more elements selected from Aland Li.
 8. An electrochemically active polycrystalline secondaryparticle comprising: a plurality of nanocrystals, the plurality ofnanocrystals comprising a first composition defined by the formulaLi_(1+x)MO_(2+y), wherein0.0≤x≤0.3,−0.3≤y≤0.3, and wherein M comprises nickel at greater than or equal to80 atomic percent; said plurality of nanocrystals having a size of lessthan or equal to 85 nanometers as measured by X-ray diffraction; a grainboundary between adjacent nanocrystals of said plurality of nanocrystalsand comprising a second composition having an α-NaFeO₂-type layeredstructure, a cubic structure, or a combination thereof, wherein aconcentration of cobalt in said grain boundary is greater than aconcentration of cobalt in said nanocrystals.
 9. The particle of claim 8wherein a concentration of cobalt in the nanocrystals is about 0.25 toabout 17 atomic percent, and a concentration of cobalt in the grainboundary is about 0.5 to about 32 atomic percent, each based on a totalatomic composition of the particle.
 10. The particle of claim 8 whereinM further comprises one or more elements selected from the groupconsisting of Al, Mg, Co, Mn, Ca, Sr, Zn, Ti, Zr, Y, Cr, Mo, Fe, V, Si,Ga and B, said one or more elements residing in a Li layer, a M layer,or both, of the nanocrystals.
 11. The particle of claim 8 wherein saidsize of said plurality of nanocrystals is 70 to 100 nanometers,optionally 75 to 90 nanometers.
 12. The particle of claim 8, wherein Mcomprises an atomic percent of nickel greater than or equal to 90%. 13.A method of manufacturing an electrochemically active particle, saidmethod comprising: providing a first mixture, said first mixturecomprising lithium hydroxide or its hydrate and a precursor hydroxidecomprising nickel; calcining said first mixture to a maximum temperatureof less than 700° C. to form a first material comprising a plurality ofnanocrystals having a size of less than or equal to 85 nanometers asmeasured by x-ray diffraction; combining said first material with asecond material comprising cobalt or a combination of cobalt andaluminum to form a second mixture; and heat treating said second mixtureto a second maximum temperature of 725° C. or less, to produce aparticle further comprising a grain boundary between adjacentnanocrystals, said grain boundary comprising a second compositionoptionally having an α-NaFeO₂-type layered structure, a cubic structure,or a combination thereof, wherein a concentration of cobalt in saidgrain boundary is greater than a concentration of cobalt in saidnanocrystals; and wherein the plurality of nanocrystals have a size ofless than or equal to 105 nanometers.
 14. The method of claim 13,wherein said step of calcining said first mixture comprises: increasinga temperature from about 25° C. to about 450° C. at about 5° C./minute;soaking at said temperature of about 450° C. for about 2 hours,increasing said temperature from about 450° C. to a maximum temperatureof about 650° C. to about 699° C.; and soaking at said maximumtemperature of about 650° C. to about 699° C. for about 6 hours.
 15. Themethod of claim 13 wherein said maximum temperature of said calciningsaid first mixture is 680° C. or less.
 16. The method of claim 13,wherein said average size of said plurality of nanocrystals are greaterthan or equal to 50 nanometers to less than or equal to 105 nanometers.17. The method of claim 13, wherein said particle comprises nickel at anatomic percent greater than or equal to 80%.
 18. The method of claim 13,wherein said particle comprises nickel at an atomic percent greater thanor equal to 90%.